The objective of our investigation is to determine the ensymatic mechanism involved in sutaneous catabolism. We are purifying and characterizing the major neutral proteinases of human skin and investigating their role in chemotaxis of polymorphonuclear leukocytes and inflammation in general. We have purified proteinases from human and mouse skin and have shown that these enzymes are extremely phlogistic. They induce polymorph induce polymorph accumulation by proteolytic activation of complement. Maximum chemotactic effect requires the presence of the fifth component of complement. Skin lesions of psoriasis contain microfoci of polymorphs. We have shown that psoriatic plaque epidermis contains increased amounts of a chemotactic complement dependent proteinase when compared to non-involved psoriatic skin and appropriate disease controls. Polymorph accumulation in psoriatic skin may reflect and increase in the specific activity of chemotactic proteinases. Incubation of mouse epithelial cells in culture with pemphigus antibody produces detachment of the epidermal cells. This phenomenon is related to proteinase activation in viable epidermal cells by pemphigus antibody. Cellular release is not a function of cytolysis by antibody. These experiments may suggest a unique mechanism by which antimembrane antibody effects cells.